Campylobacter spp. are the most frequently identified bacterial cause of acute diarrhea in the developed world and can cause post infectious complications such as reactive arthritis and Guillain-Barré syndrome. Reported cases in England and Wales recorded at the Health Protection Agency (now Public Health England, or PHE) have risen from approximately 58,000 in 2000 to about 65,000 in 2012. This has fueled the recent media storm regarding the prevalence of the organism in fresh chickens from supermarkets and butchers. Results as high as 73 percent of chickens testing positive for the presence of Campylobacter—according to Food Standards Agency—may come as a shock to many consumers; but for those who work in foodborne zoonoses, like Paul Wigley, PhD, professor at University of Liverpool in U.K., these levels are not a surprise.
“The reality is around one in 100 people get Campylobacter infection each year and most of these cases are associated with chicken,” comments Prof. Wigley. “The reason why Campylobacter has become the main issue in poultry microbiology is widely due to the host; it can colonize the chicken very well—the raised body temperature of birds over mammals and the low oxygen in the gut suit the bacterium well, meaning it can grow to levels of 1010 colony-forming unit per gram of intestinal content.”
The most frequently isolated Campylobacter spp. associated with human disease is Campylobacter jejuni, accounting for around 90 percent of cases, followed by Campylobacter coli, accounting for many of the remaining cases. Other species are reported (such as C. lari and C. upsaliensis), but these are rarely associated with human campylobacteriosis cases.
During the 1980s and 1990s, Salmonella enterica subspecies enterica serotype Enteritidis phage type 4 caused an epidemic that was frequently associated with the consumption of poultry meat and eggs. According to research published in the Journal of Applied Microbiology, the decline of incidence was widely attributed to the extensive vaccination of egg-laying hens against the serovar. Current efforts to reduce incidence of human campylobacteriosis cases largely focus around control strategies, such as hygiene and biosecurity measures of broiler flocks. However, this approach can only be effective if the control strategy efforts are focused throughout the food production chain, commonly referred to as farm to fork strategies. Efforts are underway into the feasibility of a vaccine for Campylobacter, however strategies are limited due to an incomplete understanding of the organism’s pathogenesis and extensive rate of horizontal gene transfer.
Approaches in Detection
If Campylobacter is detected at unacceptable levels within a flock, there is currently not a great deal poultry producers can do pre-slaughter to effectively reduce the levels, especially since there is huge concern regarding the over use of antibiotics that can lead to development of resistance.
A number of post-slaughter controls are being developed, such as freezing, irradiation, steam, or hot water treatment. However, these measures can only be effective if carried out at the right time and no recontamination event occurs.
For food producers the main weapon against Campylobacter remains surveillance through testing to properly implement control measures. In Europe the main standard observed for detection and enumeration of Campylobacter spp. from poultry is ISO 10272. Originally published in 2006, it is now currently under revision to incorporate several important changes. The basic format of testing includes selective enrichment in broth followed by selective isolation on solid media with further confirmation of characteristic colonies. One of the most important changes is the description of the detection procedure based on the sample type and purpose of the test.
The standard for detection is split into three groups: A, B, and C. This separation of testing protocols recognizes the challenge of radically different test samples and helps improve the ability to detect Campylobacter. All procedures use modified charcoal cefoperazone deoxycholate (mCCD) agar as the isolation medium but differ in the enrichment step.